A semi-batch Direct Coal Liquefaction facility was designed and constructed in order to examine the impact of process variables on coal liquefaction kinetics. A series of parametric investigations involving bituminous, sub-bituminous coals and lignite were performed. The process variables included solvent composition, catalyst to coal ratio, the intensity of turbulence, the initial dissolved hydrogen concentration, and the slurry residence time distribution. The results of these investigations showed that process variables have a significant impact on the rates of liquefaction reactions, and that reaction rates for coal and lignite are affected in a similar manner.

The overall rate and maximum extent of liquid and gas production was found to depend on the initial rate of molecular hydrogen transfer to the coal particles, and on the ratio of the intensity of turbulence to the level of catalysis. This latter finding led to the discovery of a persistent dispersed liquid phase within the coal liquefaction environment.

A reaction model, coupling these findings with a simple kinetic scheme, was found to correlate the liquefaction behaviour of bituminous and sub-bituminous coals and lignite, in diverse reaction environments. The experimental results and the reaction model were used to develop novel design criteria for Direct Coal Liquefaction Reactors. Two design optima were identified. One optimum is closely approximated by an existing process. An alternative and potentially preferable optimum is proposed.